Patent Document 1 describes such a known display device.
The vehicle display device described in Patent Document 1 employs a hologram, and enables analogue display by two light sources.
Namely, a cylindrical lens is disposed in front of a laser beam source, and a laser beam of a specific width emitted by the laser beam source is concentrated by the lens. By disposing a movably attached mirror at the position of the concentrated beam, and passing the concentrated beam through an opening portion in a dashboard to illuminate the hologram, the concentrated beam is visible to the driver as a pointer behind the windshield and in front of the driver.
Moreover, by disposing a light source closer to the driver than the position of the hologram on the upper face of the dashboard, and illuminating the hologram, a dial behind the windshield and in front of the driver is made visible to the driver.
Patent Document 2 describes another known vehicle display device. The vehicle display device described in Patent Document 2 is a vehicle display system in which light carrying information is emitted from a light emitting display means toward a windshield, such that a display image of the light is made visible to the driver. The display image of the light is formed on the surface of the windshield.
A light emitting lighting means includes an optical member that forms the display image of the light on the windshield surface. A diffusion plate is disposed on at least a portion of the windshield, and the display image is formed on the diffusion face. The diffusion face is a milky-white colored display screen.